Network Working S.E. Hardcastle-Kille Group ISODE Consortium INTERNET-DRAFT July 1992 Expires: January 1993 Representing Tables and Subtrees in the Directory Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the I-D abstract listing contained in each Internet Draft directory to learn the current status of this or any other Internet Draft. Abstract This document defines techniques for representing tables and subtrees in the OSI Directory [CCI88]. This technique is of general interest, but this work has been initiated towards the specific goal of supporting MHS use of Directory [HK92]. This draft document will be submitted to the RFC editor as a protocol standard. Distribution of this memo is unlimited. Please send comments to the author or to the discussion group . INTERNET--DRAFT Representing Subtrees July 1992 1 Representing Flat Tables Before considering specific function, a general purpose technique for representing tables in the directory is introduced. The schema for this is given in Figure 1. A table can be considered as an unordered set of key to (single or multiple) value mappings, where the key cannot be represented as a global name. There are four reasons why this may occur: 1. The object does not have a natural global name. 2. The object can only be named effectively in the context of being a key to a binding. In this case, the object will be given a natural global name by the table. 3. The object has a global name, and the table is being used to associate parameters with this object, in cases where they cannot be placed in the objects global entry. Reasons why the might not be so placed include: o The object does not have a directory entry o There is no authority to place the parameters in the global entry o The parameters are not global --- they only make sense in the context of the table. 4. It is desirable to group information together as a performance optimisation, so that the block of information may be widely replicated. A table is represented as a single level subtree. The root of the subtree is an entry of object class Table. This is named with a common name descriptive of the table. The table will be located somewhere appropriate to its function. If a table is private to an MTA, it will be below the MTA's entry. If it is shared by MTA's in an organisation, it will be located under the organisation. The generic table entry contains only a description. All instances will be subclassed, and the subclass will define the naming attribute. Two subclasses are defined: Expires: January 1993 Page 1 INTERNET--DRAFT Representing Subtrees July 1992 _______________________________________________________________________ table OBJECT-CLASS SUBCLASS OF top MUST CONTAIN {commonName} MAY CONTAIN {manager} ::= oc-table tableEntry OBJECT-CLASS SUBCLASS OF top MAY CONTAIN {description} 10 ::= oc-table-entry textTableEntry OBJECT-CLASS SUBCLASS OF tableEntry MUST CONTAIN {textTableKey} MAY CONTAIN {textTableValue} ::= oc-text-table-entry textTableKey ATTRIBUTE WITH ATTRIBUTE-SYNTAX 20 caseIgnoreStringSyntax ::= at-text-table-key textTableValue ATTRIBUTE WITH ATTRIBUTE-SYNTAX caseIgnoreStringSyntax ::= at-text-table-value distinguishedNameTableEntry OBJECT-CLASS SUBCLASS OF tableEntry 30 MUST CONTAIN {distinguishedNameTableKey} ::= oc-distinguished-name-table-entry distinguishedNameTableKey ATTRIBUTE WITH ATTRIBUTE-SYNTAX distinguishedNameSyntax ::= at-distinguished-name-table-key ____________________Figure_1:__Representing_Tables_____________________ Expires: January 1993 Page 2 INTERNET--DRAFT Representing Subtrees July 1992 1. TextEntry, which define table entries with text keys, which may have single or multiple values of any type. An attribute is defined to allow a text value, to support the frequent text key to text value mapping. Additional values may be defined. 2. DistinguishedNameEntry. This is used for associating information with globally defined objects. This approach should be used where the number of objects in the table is small or very sparsely spread over the DIT. In other cases where there are many objects or the objects are tightly clustered in the DIT, the subtree approach defined in Section 2 will be preferable. No value attributes are defined for this type of entry. An application of this will make appropriate subtyping to define the needed values. This is best illustrated by example. Consider the MTA: CN=Bells, OU=Computer Science, O=University College London, C=GB Suppose that the MTA needs a table mapping from private keys to fully qualified domain names (this example is fictitious). The table might be named as: CN=domain-nicknames, CN=Bells, OU=Computer Science, O=University College London, C=GB To represent a mapping in this table from ``euclid'' to ``bloomsbury.ac.uk'', the entry: CN=euclid, CN=domain-nicknames, CN=Bells, OU=Computer Science, O=University College London, C=GB will contain the attribute: TextValue=bloomsbury.ac.uk A second example, showing the use of DistinguishedNameEntry is now given. Consider again the MTA: Expires: January 1993 Page 3 INTERNET--DRAFT Representing Subtrees July 1992 _______________________________________________________________________ subtree OBJECT-CLASS SUBCLASS OF top MUST CONTAIN {commonName} MAY CONTAIN {manager} ::= oc-subtree ___________________Figure_2:__Representing_Subtrees____________________ CN=Bells, OU=Computer Science, O=University College London, C=GB Suppose that the MTA needs a table mapping from MTA Name to bilateral agreement information of that MTA. The table might be named as: CN=MTA Bilateral Agreements, CN=Bells, OU=Computer Science, O=University College London, C=GB To represent information on the MTA: CN=Q3T21, ADMD=Gold 400, C=GB There would be an entry in this table with the Relative Distinguished Name of the table entry being the Distinguished Name of the MTA being referred to. The MTA Bilateral information would be an attribute in this entry. 2 Representing Subtrees A subtree is similar to a table, except that the keys are constructed a a distinguished name hierarchy relative to the location of the subtree in the DIT. The subtree effectively starts a private ``root'', and has distinguished names relative to this root. Typically, this approach is used to associate local information with global objects. The schema used is defined if Figure 2. Functionally, this is equivalent to a table with distinguished name keys. The table approach is best when the tree is very sparse. This approach is better for subtrees which are more populated. Expires: January 1993 Page 4 INTERNET--DRAFT Representing Subtrees July 1992 The subtree object class defines the root for a subtree in an analogous means to the table. Information within the subtree will generally be defined in the same way as for the global object, and so no specific object classes for subtree entries are needed. For example consider University College London. O=University College London, C=GB Suppose that the UCL needs a private subtree, with interesting information about directory objects The table might be named as: CN=private subtree, O=University College London, C=GB UCL specific information on Inria might be stored in the entry: O=Inria, C=FR, CN=private subtree, O=University College London, C=GB Practical examples of this mapping are given in [HK92]. References [CCI88] The Directory --- overview of concepts, models and services, December 1988. CCITT X.500 Series Recommendations. [HK92] S.E. Hardcastle-Kille. MHS use of the directory to support MHS routing, April 1992. Internet Draft. 3 Security Considerations Security considerations are not discussed in this INTERNET--DRAFT . 4 Author's Address Steve Hardcastle-Kille Expires: January 1993 Page 5 INTERNET--DRAFT Representing Subtrees July 1992 ISODE Consortium PO Box 505 London SW11 1DX England Phone: +44-71-223-4062 EMail: S.Kille@ISODE.COM DN: CN=Steve Hardcastle-Kille, O=ISODE Consortium, C=GB UFN: S. Hardcastle-Kille, ISODE Consortium, GB Expires: January 1993 Page 6 INTERNET--DRAFT Representing Subtrees July 1992 A Object Identifier Assignment _______________________________________________________________________ mhs-ds OBJECT-IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1) private(4) enterprises(1) isode-consortium (453) mhs-ds (3)} tables OBJECT IDENTIFIER ::= {mhs-ds 1} oc OBJECT IDENTIFIER ::= {tables 1} at OBJECT IDENTIFIER ::= {tables 2} oc-subtree OBJECT IDENTIFIER ::= {oc 1} oc-table OBJECT IDENTIFIER ::= {oc 2} 10 oc-table-entry OBJECT IDENTIFIER ::= {oc 3} oc-text-table-entry OBJECT IDENTIFIER ::= {oc 4} oc-distinguished-name-table-entry OBJECT IDENTIFIER ::= {oc 5} at-text-table-key OBJECT IDENTIFIER ::= {at 1} at-text-table-value OBJECT IDENTIFIER ::= {at 2} at-distinguished-name-table-key OBJECT IDENTIFIER ::= {at 3} _______________Figure_3:__Object_Identifier_Assignment_________________ Expires: January 1993 Page 7